Emerging Inorganic Solid-State Electrolytes Membrane Technologies for Innovative Lithium Separation

Increasing global demand for lithium has driven the development of innovative extraction technologies for a wide range of resources that are sustainable and selective. Inorganic solid-state electrolytes (ISSEs), originally designed for lithium–ion batteries, have recently emerged as promising materials for membrane-based lithium separation due to their high lithium–ion conductivity, structural stability, and inherent ion selectivity. This review highlights recent advances in ISSE membranes for lithium recovery from complex aqueous sources, such as seawater and brine. The crystallographic frameworks of representative ISSEs, such as garnet-, NASICON-, and perovskite-type structures and their lithium–ion transport mechanisms, are discussed in detail. Particular attention is given to electrochemically mediated systems that leverage applied electric fields to drive the selective transport of lithium through ISSE membranes. Furthermore, we discuss structural modifications and interfacial engineering strategies to enhance selectivity and conductivity as well as the development of flexible ISSE–polymer composite membranes that improve mechanical stability and scalability. Despite notable progress, challenges in interface optimization, long-term durability, and large-scale manufacturing remain. This review provides future research directions for advancing ISSE-based lithium separation technologies as energy-efficient, selective, and scalable solutions for sustainable lithium production.